1. Field of the Invention
The present invention relates to a filling channel opening and closing device that opens and closes a filling channel at a predetermined timing in a liquid product filling apparatus used to fill containers with liquid product supplied from a liquid product storage tank and more particularly to a filling channel opening and closing device that opens and closes a filling channel by collapsing with an external force a flexible tube installed as part of the filling channel and causing it to restore.
2. Description of Related Art
Japanese Patent Nos. 3704270 and 3454875 and Japanese Patent Application Laid-Open (Kokai) Nos. 2008-94496 and 2009-234633 disclose filling channel opening and closing devices. In these devices, a flexible tube made of an elastic material is installed in a filling channel, as part of this filling channel so that it is located between a liquid product storage tank and the discharge orifice of a filling nozzle (including a filling nozzle), and a rigid pressing member, which advances and retracts by a driving source, is disposed in the vicinity of the flexible tube. In such a filling channel opening and closing device, the driving source causes the pressing member to advance to apply pressure to the flexible tube, thereby collapsing the flexible tube to close the filling channel at the flexible tube portion. On the other hand, when the filling channel is to be opened, the pressing member is retracted and separated from the flexible tube, thus causing the flexible tube to restore (to its original shape) to open the filling channel. It these operations, the restoring of the flexible tube takes place under the action of the pressure of the liquid inside the filling channel (or inside the flexible tube) and the restoring force of the flexible tube itself (if it is formed from an elastic material).
In the filling channel opening and closing devices described above, the direct contact and separation of the pressing member with respect to the flexible tube is repeated whenever the filling channel is opened and closed (during each filling operation), and this results in considerable localized wear in the flexible tube at the location(s) of contact. For this reason, it is necessary to replace the flexible tube frequently, which is problematic in terms of cost and imposes a heavy burden on the operator. In addition, the wear of the flexible tube results in, among others, contamination, creating problems in terms of its cleaning and maintenance properties.